var show_num = [];

(function(){
    draw(show_num);
    $("#canvas").on('click',function(){
        draw(show_num);
    });
    //单击事件的时候校验输入的验证码是否正确
    //可以将此段代码放在外围
    /*$("#Logincode").on('click', function() {
        var val = $(".input-val").val().toLowerCase();
        var num = show_num.join("");
        if (val == '') {
            alert('请输入验证码！');
        } else if (val == num) {
            alert('验证码校验成功！');
            $(".input-val").val('');
            draw(show_num);
        } else {
            alert('验证码错误！请重新输入！');
            $(".input-val").val('');
            draw(show_num);
        }
    })*/
})();


function draw(show_num) { //显示区域内容信息
    var canvas_width = $("#canvas").width();
    var canvas_height = $("#canvas").height();
    var canvas = document.getElementById("canvas"); //获取到canvas的对象，演员
    var context = canvas.getContext("2d"); //获取到canvas画图的环境，演员表演的舞台
    canvas.width = canvas_width;
    canvas.height = canvas_height;
    var sCode =
    "a,b,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,W,X,Y,Z,1,2,3,4,5,6,7,8,9,0";
    var aCode = sCode.split(",");
    var aLength = aCode.length; //获取到数组的长度

    for (var i = 0; i <= 3; i++) {
            var j = Math.floor(Math.random() * aLength); //获取到随机的索引值
            var deg = Math.random() * 30 * Math.PI / 180; //产生0~30之间的随机弧度
            var txt = aCode[j]; //得到随机的一个内容
            show_num[i] = txt.toLowerCase();
            var x = 10 + i * 20; //文字在canvas上的x坐标
            var y = 20 + Math.random() * 8; //文字在canvas上的y坐标
            context.font = "bold 23px 微软雅黑";

            context.translate(x, y);
            context.rotate(deg);

            context.fillStyle = randomColor();
            context.fillText(txt, 0, 0);

            context.rotate(-deg);
            context.translate(-x, -y);
    }
    for (var i = 0; i <= 5; i++) { //验证码上显示线条
        context.strokeStyle = randomColor();
        context.beginPath();
        context.moveTo(Math.random() * canvas_width, Math.random() * canvas_height);
        context.lineTo(Math.random() * canvas_width, Math.random() * canvas_height);
        context.stroke();
    }
    for (var i = 0; i <= 30; i++) { //验证码上显示小点
        context.strokeStyle = randomColor();
        context.beginPath();
        var x = Math.random() * canvas_width;
        var y = Math.random() * canvas_height;
        context.moveTo(x, y);
        context.lineTo(x + 1, y + 1);
        context.stroke();
    }
}

function randomColor() { //得到随机的颜色值
    var r = Math.floor(Math.random() * 256);
    var g = Math.floor(Math.random() * 256);
    var b = Math.floor(Math.random() * 256);
    return "rgb(" + r + "," + g + "," + b + ")";
}